Laugh at the eighty-one difficult joke

It's all allusions to Monkey Sun. My personal understanding is that Monkey Sun refers to life, trying to practice the art of benefiting things and living in peace, and smiling at the joys and sorrows of life. The six-year-old boy said this because he had been playing the Monkey King all his life, and his world outlook was greatly influenced by the Monkey King, so he used an allusion from the Monkey King to explain his philosophy of life.